The Streptococci make up a medically important genera of microbes known to cause several types of disease in humans, including, for example, otitis media, conjunctivitis, pneumonia, bacteremia, meningitis, sinusitis, pleural empyema and endocarditis, and most particularly meningitis, such as for example infection of cerebrospinal fluid. Since its isolation more than 100 years ago, Streptococcus pneumoniae has been one of the more intensively studied microbes. For example, much of our early understanding that DNA is, in fact, the genetic material was predicated on the work of Griffith and of Avery, Macleod and McCarty using this microbe. Despite the vast amount of research with S. pneumoniae, many questions concerning the virulence of this microbe remain. It is particularly preferred to employ Streptococcal genes and gene products as targets for the development of antibiotics.
The frequency of Streptococcus pneumoniae infections has risen dramatically in the past 20 years. This has been attributed to the emergence of multiply antibiotic resistant strains and an increasing population of people with weakened immune systems. It is no longer uncommon to isolate Streptococcus pneumoniae strains which are resistant to some or all of the standard antibiotics. This has created a demand for both new anti-microbial agents and diagnostic tests for this organism.
The peptide release factor, prfC (RF-3), is one of three factors required for the termination of protein synthesis in bacteria. RF-3 is a GTP-binding protein that displays sequence similarity to GTP-binding proteins. RF-3 stimulates the activities of RF-1, which has been shown to be essential in vitro (Olafsson et al 1996: J. Bacteriol 178(13) 3829-39), and RF-2 but is not codon specific. Mutations in RF-3 causes suppresion of all three stop codons in vivo (Mikuni et al (1994) PNAS 91, 5798-5802). This information warrants the further investigation of RF-3 as a potential novel antibacterial target.
Clearly, there is a need for factors, such as the novel compounds of the invention, that have a present benefit of being useful to screen compounds for antibiotic activity. Such factors are also useful to determine their role in pathogenesis of infection, dysfunction and disease. There is also a need for identification and characterization of such factors and their antagonists and agonists which can play a role in preventing, ameliorating or correcting infections, dysfunctions or diseases.
The polypeptides of the invention have amino acid sequence homology to a known E. coli RF-3 (prfC) protein.